This invention relates to containers for storing and transporting disks. More particularly it relates to such a container with a low particle generating latching mechanism.
Wafers and disks are utilized in the semiconductor industry for processing into circuit chips and magnetic storage disks. The wafers are typically made of silicon or other materials and are subjected to many processing steps before they become integrated circuits. Similarly magnetic storage disks may be made of metal and are also subjected to a number of processing steps. Such magnetic storage disks or wafers must be transported from place of manufacturer to processing facilities and must be transported within such processing facilities. The silicon wafers are particularly fragile and there is always the concern for breakage and/or other damage. The wafers and disks are typically transported in plastic containers adapted for providing a generally sealed enclosure along with providing secure retention and cushioning means for the wafers. It is critical for both wafers and magnetic disks that the enclosure be very clean and preclude entry of particles or other containments. Any particles or other containments in the containers can adhere to the disks or wafers causing damage or necessitating additional cleaning steps.
Containers for magnetic storage disks have become generally standardized their general configuration as shown in Prior Art FIGS. 1, 2, 3, 4, and 5. Such storage disk containers have three principal parts, a cassette 20, a top cover 22 and a bottom cover 24. These component parts are generally molded from thermoplastic materials such as polycarbonate, polypropylene and the like.
The cassette is generally boxed shaped with an open top 26, an open bottom 28, a plurality of slots 30 to in the side walls 34 for holding the disks in an axial arrangement. U-shaped recesses 36 extend downwardly from the top edge 38 into the endwalls 40 allow axial access to the disk apertures.
The top covers generally have rectangular top portion 42 and two end portions 44 which extend downwardly from the top portion. The end portions close the openings 46 in the endwalls. Different means have been utilized to latch the top cover 22 to the cassette 20. One such latching means is shown in the Prior Art FIGS. 1 and 2 and is disclosed in U.S. Pat. No. 4,557,382 to Douglas Johnson. This embodiment utilizes end portions that extend slightly inward to create an interference fit with the cassette. The end portions must be flexed outwardly for the top cover to be lowered and placed on the cassette. The end covers are then held in placed by the spring action of the end portions and also by a frictional engagement. One disadvantage of the top cover latching mechanism of FIGS. 1 and 2 is that the inwardly extending ends can creep outwardly over time such that no spring action is provided for the latching. Additionally, some level of finesse is required to lower the top cover onto the cassette without making scrapping contact between the end portions 44 and with any disks in the cassette or with the rims 50 of the endwalls. Additionally, there have been concerns that the end portion 44 engagement by the lip 49 with the rim 50 does not create a secure latch or an adequate seal particularly around the entire length of said rim 50.
Referring to Prior Art FIGS. 3, 4, and 5 an embodiment is shown which is representative of the invention of the U.S. Pat. No. 5,253,755 to Dale A. Maenke. In this disk container the top cover 22 has a structural offset portion 54 which is shaped to follow the curvature 56 of the U-shaped recess 36 and rim 50. This structural offset thus forms a labyrinthine seal with respect to the path 55 between the end portions 44 of the top cover 22 and the endwalls 40. In the disk container 18 shown in FIGS. 3, 4, and 5 the top cover is lowered down to the cassette such as with one hand and snaps into the engagement position as shown in FIG. 5. The ramped surface 58 engages the rim 50 as it is being lowered down and continued downward pressure on the top portion of the top cover urges the engagement member 60 outwardly to clear the rim to the latched position as shown in FIG. 5. Although this particular latching arrangement and top cover configuration has generally been accepted by the industry, concerns have been raised that such a snap-in top cover operates to launch particles from the top cover and cassette during the snap action. Said particles would thus be airborne to and may end up as containments on the magnetic disks. Therefore it is desirable to have a latching mechanism that is not subject to the creep and sealing problems associated with the embodiment in FIGS. 1 and 2 and that also does not utilize the snap action of the embodiments of FIGS. 3, 4, and 5.